The long term objectives of the research described in this competing continuation application remain the clarification of the relationship between the development of resistance to chemotherapeutic agents, specifically Adriamycin, and change in radiation response; to determine the role of cell membrane in the expression of radiation damage by the use of drug-resistant membrane variants; and to study the damage interactions between chemotherapeutic agents and radiation in drug- resistant cell populations. The working hypothesis is that the cell membrane represents an important structure with regard to the cytotoxicity of certain chemotherapeutic agents, particularly Adriamycin, and that the interaction between Adriamycin and radiation damage occurs predominantly in that structure. Chinese hamster lung fibroblasts (V-79) and their Adriamycin-resistant variants will be used throughout these studies. Radiation, Adriamycin, and combination survival curves will be determined. Cell membrane preparations will be isolated form both sensitive and Adriamycin-resistant cells and a partially purified preparation of a glycoprotein of 170,000 daltons fused to sensitive cells. Adriamycin, radiation, and Adriamycin/radiation survival responses will be determined in the fusion products. The presence or absence of the high molecular weight glycoprotein will be determined in the fusion products. The presence or absence of the high molecular weight glycoprotein will be determined with 1-dimensional electrophoretic techniques. Intracellular and membrane-bound Adriamycin will be determined fluorometrically utilizing the fluorescence of the chromphore. The time-course of gp170 persistence in fusion products will be determined by radiation and/or Adriamycin survival responses as a function of time after fusion. In addition to single dose radiation responses, studies will be designed to test the capacity of Adriamycin-resistant cells and fusion products, as described above, to repair sub-lethal or potentially lethal radiation injury. If the long term objectives of the research described in this proposal are realized, the data may provide important information relative to the mechanisms of the development of resistance to chemotherapeutic agents, the radiation response of such resistant cells, and the possible genetic control of these mechanisms. Such information may have important implications in the treatment of patients who have failed chemotherapy and the prediction of subsequent radiation response of drug-resistant tumor cells.